Poly(arylene ether) resins are a class of plastics known for excellent water resistance, dimensional stability, and inherent flame retardancy, as well as high oxygen permeability and oxygen/nitrogen selectivity. One property challenge posed by poly(arylene ether) is its poor melt processability. The most common solution to the problem of poor melt processability is to blend the poly(arylene ether) with polystyrene or another styrenic resin. The disadvantage of this solution, however, is that such blending leads to inferior heat resistance, flame retardancy, and smoke generation relative to pure poly(arylene ether).
Other approaches involve the blending of poly(arylene ether)s with polysiloxanes in various forms. For example, as described in U.S. Pat. No. 5,916,952 to Romenesko et al., a poly(phenylene ether) can be blended with a free-flowing silicone rubber powder having an average particle size of 1 to 1000 microns and prepared by mixing a polydiorganosiloxane with a silica filler. However, these compositions can exhibit phase separation and inadequate flexibility.
Another example involves blending of poly(arylene ether) with polysiloxane-modified polystyrene to achieve improved processability along with improved mechanical properties. See U.S. Pat. No. 4,226,761 to Cooper et al. The polysiloxane-modified polystyrene is prepared by dissolving the polysiloxane in styrene and polymerizing the styrene. However, these compositions can exhibit poor flexibility.
Poly(arylene ether) compositions have also incorporated polysiloxane content in the form of poly(arylene ether)-polysiloxane block and graft copolymers. Syntheses of poly(arylene ether)-polysiloxane block and graft copolymers include the following four approaches. First, a graft copolymer has been synthesized by reaction of a lithiated poly(arylene ether) with a polydiorganosiloxane having a reactive group on one end. See Japanese Patent Application Publication No. JP 61-252214 of Matsui et al. Second, a graft copolymer has been synthesized by reaction of an anhydride-functionalized poly(arylene ether) with an amino-terminated polydiorganosiloxane. See U.S. Pat. No. 4,814,392 to Shea et al. Third, a block copolymer has been synthesized by reacting a poly(arylene ether) with a hydroxyaromatic-terminated or aromatic ether-terminated polysiloxane reagent in the presence of an oxidant. See U.S. Pat. No. 5,596,048 to Blohm et al. Fourth, a poly(arylene ether)-polysiloxane block copolymer has been synthesized by reaction of a poly(arylene ether), a hydroxyaryl-terminated polysiloxane, and an activated aromatic carbonate. See U.S. Patent Application Publication No. 2007/0208144 A1 of Delsman et al. These synthetic procedures have various disadvantages. In some cases, they require multiple synthetic steps and employ expensive and sensitive reagents and they are therefore not economically suited for commercial-scale syntheses. Also, some of the poly(arylene ether)-polysiloxane copolymer products exhibit poor thermal and hydrolytic stability, due to the presence of C—O—Si linkages. Furthermore, some of the product copolymers have undesirably low molecular weights.
There is therefore a desire for poly(arylene ether) copolymers that can be made by a simplified procedure and exhibit increased molecular weight and improved thermal and hydrolytic stability.